Water and/or alcohol, such as Water/Methanol/Ethanol (WME) may be injected, alone or in combination, into cylinders of a spark-ignition engine in order to increase operating efficiency, fuel economy, and/or operational life of the engine. For example, WME may be injected into a cylinder to reduce peak cylinder temperature/pressure. By lowering peak cylinder temperature/pressure, cylinder degradation may be reduced to increase the operational life of the engine. As another example, WME may be injected into a cylinder to suppress engine knock. By suppressing engine knock, the engine may be operated at a higher compression ratio to permit higher engine output or increased fuel economy. Further, WME may be injected into a spark-ignition engine to reduce tailpipe emissions. For example, WME may be injected into a cylinder to reduce exhaust/emission control device temperature (e.g. catalyst). By reducing exhaust emission control device temperature, the emission control device temperature may be maintained within a desired temperature range to improve conversion of feedgas emissions.
Various strategies and configurations may be implemented to inject WME into cylinders of a spark-ignition engine in order to achieve the above described benefits. In one example approach, a dual fuel injection system in which each cylinder includes a direct injection (DI) injector and a port injection (PI) injector is reconfigured so that the DI injector is dedicated to injecting WME and the PI injector is dedicated to injecting a type of fuel. Accordingly, fuel can be injected via port injection to handle engine torque demands, while WME can be injected via direct injection to improve engine operating efficiency, fuel economy, emission control, etc. The DI injector may be dedicated to injecting WME because direct injection may improve vaporization of the injected fluid relative to port injection. Such vaporization may be beneficial for dealing with certain conditions, such as to suppress engine knock.
However, the inventors have recognized several potential issues with such an approach. For example, to improve vaporization/atomization of injected fluids, fluids need to be delivered to injectors at high pressure at startup, dual injection systems include a high pressure positive displacement pump to increase the pressure of fluid injected by the DI injector to a suitable injection pressure level. The high pressure pumps can be expensive to manufacture and may increase the production cost of the engine.
The inventors herein have developed a system that may provide the above benefits at lower expense. For example, the system may include an internal combustion engine having a combustion chamber, a first injector to provide a first injection fluid to the cylinder, and a heated pressurization system to heat the first injection fluid in a pressure vessel to a specified temperature for injecting the first injection fluid to the cylinder by the first injector at a specified injection pressure.
As an example, the first injection fluid may be a composition of alcohol and water that may be directly injected to the cylinder in response to high cylinder temperature/pressure, engine knock, etc. By heating the injection fluid in a pressure vessel, pressure in the vessel can be increased to the specified injection pressure. In this way, the injection fluid may be provided at the injection pressure without the use of a costly high pressure positive displacement pump, although a pump may additionally be used, if desired. Accordingly, the high pressure positive displacement pump may, in some cases, be omitted from the engine and the production cost of the engine may be reduced.
It will be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description, which follows. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined by the claims that follow the detailed description. Further, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.